Effect of vacuum leaks on throttle response

[Slacky28]

Any thoughts before I spend money at a MB Dealer?

I have recently acquired a W203 2001 C220 CDi Estate Auto which I am surprisingly passionate about.

And this unexpected passio has led to me blowing 3 times the budget I had set aside to bring this 173k-er back to scratch. From Cleaned out EGr's and Autobox to new antiroll bars and rust removal/repainting.

But it does have an annoying, potentially dangerous trait of waiting for a couple of seconds when at stanstill between hitting the throttle and the old dear actually moving.

On the sunny bank holiday just gone I met a man (a mechanic) who knew and had driven the car, who felt that this may be a leak in the vacuum system. His hunch at the headlight adjustment end?

And in turn, issues with engine components such as the wastegate which might account for the slugish (at best) reaction to the lights turning green.

Anyone?

 

[television]

Yes Diesel do not have a vacuum system on the engine, you have a pump driven from the engine to operate the lamps and other things.

So not that

 

[Slacky28]

Thank you, appreciated. Any thoughts then? There is loads on the interweb about this problem but no consistent set of causes. Pretty sure it's not the Cat!

 

[television]

Sadly I am not a diesel man, and hopefully someone will answer you problem

 

[turbopete]

MAF? does the car rev as expected but not move, or does it just not do anything until it sets off? Auto's arent really my thing, but it could be in need of a transmission fluid change or similar

 

[Cole@MBS]

There is a vacuum system on the 203, its pulled from the brake booster, it controls the egr and turbo, as well as headlights and rear head rest droppers, a simple brake anywhere in this system cause a major fault and be logging fault codes and putting the engine light on.....

 

[Slacky28]

Thank you all - apologies

Sorry all above and belated thankyou - I was not picking up any post notices after first from Television. Possibly updated spam software.

In answer to some... I have cleaned out the EGR, the Gearbox Fluid and Filter, and had a +31 BhP remap from Black Code (+ figure theirs, dyno'd from same age/model car; and I believe them).

V pleased with results of all. Black Code remap replaced a Commonrail booster plug-in which cost more but was inferior by far to the proper remap (cos it now feels like a natural car, not a boosted one, even tho results are actually better).

But STILL this bl@@dy "Oh, he has pressed the accelerator, let's translate that into German and tell the ECU" to, er, GO (schnell bitte, errrr, please.... there's a lorry coming round the roundabout!) problem from standstill.

Black Code think it's a problem with the Pedal Value Sensor. The guy who looked after it for previous owner said Vacuum. Local MB dealer patronisingly disparaged forums and said he doubted there was a problem at all (because his senior tech drove it to fix an earlier problem and never mentioned it).

Unhappy, confused and basically... I love this car except it makes me panic at roundabouts and T Junctions. I don't want it to be a 911 (been there). I just want it to go... reasonably smartly, when I ask it to.

Slacky

 

[Slacky28]

ps... it's not gearbox, the engine revs fine with no restrictions (apart from engine breaking, using the gears helps a bit (I'm using 2 and 3 at "difficult junctions). it accelerates beautifully at kickdown for overtaking (with a small lag still). There is no symptom other than "having a little conversation with itself" before obeying what the throttle is mechanically telling it to do. The slower the speed, the more pronounced, from standstill... dangerously slow in my opinion!

 

[BachelorDays]

Pedal sensor would be a reason. You could exclude the MAF from all this by disconnecting it and taking it around the block. Does it happen when engine cold as well?

 

[DY2]

Had a vacuum leak on my C220... I found it to be a split, in a small rubber hose, next to the oil filter housing..

http://img.photobucket.com/albums/v661/DY2/IMG00812-20120128-1345.jpg

You can see the grey tape bandage...

Just a small 2-3 inch rubber hose, which pulls off.... Worth checking

 

[Carl@MBS]

To be fair the diesels don't have an instant response, have you driven others to confirm its worse than normal?

 

[oigle]

My 270 motor in my ML had similar issues from new - positively dangerous on roundabouts etc with lack of immediate response. I had my ecu remapped to fix it (and it did). I wonder if your rempap or whatever you had done has not been done well in that area?
As an aside, people who have deleted the egr from the system have found throttle response to be considerably better afterwards. Worth doing anyway for many other reasons.

 

[alexanderfoti]

A throttle pedla sensor will cause this as well, a leaking vaccum system wouldnt cause hesistation (but would cause lots of other issues as mentiond)